My test setup using an inexpensive low power (10-30 Volt 10 amp) PWM motor controller to drive a bank of high power STP75NF75 MOSFETs looks very promising. These MOSFETs are rated 75 Volts and 80 AMPS so I plan to parallel at least 6 of them for 480 AMPS. The Battery Bank will be only 48 volts, which is sufficient for the ME0709 motor in my sailboat installation.
In my test set-up I used a 400V 70 Amp blocking diode to across the motor leads to block the reverse EMF and a 1000 ohm resistor to maintain the MOSFET gate at ground when not energized by the controller. The unloaded motor responded very well over full range of controller. Questions for electronic experts:
1. 1. Can I just simply parallel the MOSFETs on a single heat sink or do I need some resistive isolation between them on the gates?
2. 2. What else should I use to protect the MOSFETs from transients? More diodes? Zener diodes? Capacitors? Have seen various written advice
3. 3. If I assume all motor starts will be ramped up from low levels, and there will be no starting surge it does not seem that I need pre-charge capacitors found with many commercial controllers. Is this correct or am I missing something?
Thanks in advance for any suggestions.
Art
Posted by: jortlif@msn.com
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